The Human Condition, published in 1958, is one of the central theoretical works of the philosopher and political theorist Hannah Arendt. It is an account of the historical development of the situation of human activity, from the Ancient Greeks to modern Europe. This book is not to be confused with André Malraux's novelLa Condition humaine (1933), the title of which has been translated into English as Man's Fate; to avoid confusion, Arendt’s book was translated in French as Condition de l’homme moderne (The Condition of the Modern Man).

Arendt aims the book at the possibilities of the vita activa (the title she preferred) in the modern world. She defines the three activities – labor, work, and action – and describes four possible realms: the political, the social, the public, and the private. She then explains how the Ancient Greeks positioned each activity in each realm, and criticises the modern world from this standpoint.

Arendt introduces the term vita activa (active life), by distinguishing it from vita contemplativa (contemplative life), which represent a vision of how life should be lived. The vita activa comprises three human activities – labor, work, and action – which correspond to the three basic conditions under which humans live. Action corresponds to the political actions of free citizens, particularly in the ancient Greek Polis. This is evident in Aristotle's definition of man as a "political animal" ("ὁ ἄνθρωπος φύσει πολιτικὸν ζῷον") which was translated as 'animal sociale' or "social animal" by Seneca and medieval writers, while the word "social" did not exist in ancient Greek vocabulary. Likewise, starting with Plato, philosophy began to see itself as following the vita contemplativa and aiming to experience the eternal, outside and above the political sphere. Action, according to Arendt, aims to offer an alternative: attaining immortality through political activity.

Arendt points out that the "human condition" and "human nature" are not synonymous. She draws a distinction between them by explaining that, if humans were to colonize the moon or some other planetary body, they would live under new conditions. Their human nature, however – if there is such a thing – would remain intact. Human nature is located within human beings; the human condition related to their living together in the world.

According to Arendt, life for the ancient Greeks was divided between two realms: that of the public, in which political activity was performed and democracy could be realised, and that of the private, site of property and family life where the father ruled like an absolute monarch. It was in the public realm alone where, as first expressed by Aristotle, true freedom could be attained through "great words and great deeds" in the same way as personal glory could be attained in the battlefield. In this respect Arendt noted that Athenian Democracy was not really the realm of the many, as it is commonly thought, but of the one, who through powerful words and deeds could leave his mark on the world and as this world was thought to be immortal, the man who would leave his mark in it would also pertain in its immortality. The private realm on the contrary, is the realm for necessity. It is located in the "shadowy interior of the household" which consisted of women, children and slaves. All the activities concerning the subsistence of human lives are operated here, including production, reproduction, economy, etc. Slaves, in this respect, were people whose lives were entirely ruled by necessity, both theirs and their masters. Violence is the tool to maintain a household which belongs to the head (oikonomon in Greek). Private affairs can be charming but never glorious and this is why they were naturally excluded from the public debate in the ancient Agora. Since the Roman Age, a third realm has come into being: the social. In relation to the other two, society is simply a collection of private needs in one entity and is therefore comparable to the household. Both the social and private therefore are realms of necessity, the need to sustain one's own body through labor (explained below) and that of their family. The public sphere in contrast starts where necessity ends and this is why the citizens of city-states would try to alleviate themselves from it as much as possible (often using slaves) in order to enter it. Once there, these citizens would debate on issues above and beyond everyday sustenance and bereft of personal or private interests. Topics would include the public affairs which concerned everyone such as education, war and law. Violence is totally excluded from this sphere where glory comes from one's successful persuasion of others with one's own reason and rhetorical power.

Arendt admits that her distinction is unusual as it has not been attempted previously by the thinkers who concerned themselves with the subject, like for instance Karl Marx, yet it cannot be ignored. Labor is one of the three fundamental forms of activity that form the vita activa. It is repetitive, never-ending and only includes the activities that are necessary to the sustenance of life, such as the production of food and shelter as well as physical reproduction, with nothing beyond that. The condition to which labor corresponds is sheer biological life. Socially, it was the type of life that was destined for slaves in the Ancient Greek city-states. Within this life-world, slaves were considered as such not due to the harshness of their lives but mainly because these lives were composed of necessity alone, as a sum of their own physical needs and the ones of their masters added on it. The products of Labor is thus consumed as soon as it is produced without leaving any lasting trace behind. Work on the other hand, being the second activity, has a clearly defined beginning and end. It leaves behind an enduring artefact such as a tool, a manuscript, or a building. The condition to which this activity corresponds is the World and was socially connected with the free citizens of the ancient city-states, especially their acts in the realm of politics they were called to undertake. As the ancient world-view which sustained these concepts gave way to the modern however, political life waned and the private life of necessity entered the public realm. This led Labor out of the constraints of the household to become a significant value on its own right. In modern day democracies therefore, the concept of equality which is considered to be one of its pre-conditions, has been skewed into one of similarity as it is now based on common necessity, the realm of Labor. Arendt points out that equality can only be applied to things that are unequal like the distinct personalities of free citizens. Necessity is what is similar to humans and thus equating people under Labor is not real equality but a kind of debasement.

The third activity, that of great deeds and great words, is specifically political and properly construed can only take place in the public realm potentially leading to the only form of immortality properly accepted in ancient Greece, that of creating something lasting within the world. This world is also made common through action. It necessitates speech (logos), since the actor needs to declare his or her unique existence in order for that action to be considered human. Other actions exist of course, such as bartering goods in a market, that do not require such a unique declaration. These, however, are products of the subject's necessity (ex. obtain food to survive) and not some unique individuality which is properly his. In this sense, worker's equality is almost a tautology, since it equates people through the basic human condition of need, while citizen's equality is by definition equality of unequals that are trying to create a common world. Its corresponding conditions are natality and plurality. Action can never manifest through a predictable, deterministic series of consequences, since the subject, by acting, is placed within a complicated web of relationships which cannot be predicted before hand. In the same sense, Action is irreversible.

Arendt records the decline of what the Ancient Greeks understood as the Public Sphere, as a place where immortality can be attained through great works and lasting deeds. This happened mainly through a shift of focus from the immortality of the human world into abstract concepts of the mind, as the importance of the human senses as a source of objective knowledge about the world declined. "Cartesian doubt", as she calls the notion that a person's senses could be presenting him with a false world, an illusion, possibly created by some malevolent god (dieu trompeur), is best expressed in the phrase cogito ergo sum (I think, therefore I exist), meaning that the only thing a person can be certain of is not the world around him but his own cognitive process. This great shift prepared the world for Galileo's heliocentric universe in which the possibility of attaining immortality through lasting deeds (Action) was completely lost. Arendt also observes the evolution of scientific thinking from the "world-bound" geometry of the ancient world, to the abstract concepts of algebra without which Newton could never have formulated his Universal Laws.